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That is P1/P2=V2/V1
2. Gay Lusack's law When the pressure P is constant, the volume V of a certain mass of gas is proportional to the absolute temperature T:
V1/V2=T1/T2=Constant When the pressure is constant, a certain mass of gas will increase (or decrease) by 1/273 the original volume when the temperature rises (or P decreases) by 1°C.
3, Charlie's law When the volume of gas V remains unchanged, a certain quality of gas, pressure P is proportional to its absolute temperature T, that is:
P1/P2=T1/T2
In a certain volume, a certain mass of gas increases (or decreases) its pressure by 1/273 every time it increases (or decreases) by 1°C.
4, the average free path:
λ=(5×10-3)/P(cm)
5, pumping speed:
S=dv/dt (l/s) or S=Q/P
Q = flow (Torr · liters / second) P = pressure (Torr) V = volume (l) t = time (seconds)
6, through the guide: C = Q / (P2-P1) (liter / second)
7, vacuum pumping time:
For atmospheric pressure to 1 Torr evacuation time formula:
t=8V/S (empirical formula)
V is the volume and S is the pumping rate. Usually t is selected within 5 to 10 minutes.
8, maintain the pump selection:
S dimension = S first/10
9, diffusion pump speed estimation:
S = 3D2 (D = diameter cm)
10, the pumping speed of the Roots pump:
S=(0.1~0.2)Sro (l/s)
11, leakage rate:
Q leakage = V(P2-P1)/(t2-t1)
Q Leakage - System Leakage Rate (mmHg·l/s)
V-system volume (l)
P1 - System pressure (mmHg) when the vacuum pump is stopped
P2 - Pressure reached after time t passes through the vacuum chamber (mmHg)
T-pressure rise time from P1 to P2 (s)
12, pumping speed selection of rough pump:
S = Q1/P pre (l/s)
S=2.3V·lg (Pa/P pre)/t
S-mechanical pump effective pumping speed Q1-vacuum system leak rate (Torr·l/s)
P Pre-Required Pre-vacuum (Torr)
V-vacuum system volume (l)
t - the time required to reach P pre-time Pa - atmospheric pressure (Torr)
13. Foreline pumping speed selection:
Transmission pumps with exhaust outlet pressures lower than one atmosphere, such as diffusion pumps, oil boosters, Roots pumps, turbomolecular pumps, etc., require a foreline pump to maintain their foreline pressure below a critical value. The pump must be able to discharge the maximum volume of the main pump. According to the principle of constant flow in each section, the following principles are:
PnSg≥PgS or Sg≥Pgs/Pn
Sg-effective pumping speed of the pre-pump (l/s)
Pn-critical upstream pressure of the main pump (maximum exhaust pressure) (l/s)
Pg-vacuum chamber maximum working pressure (Torr)
S - The effective pumping speed at Pg when the main pump is operating. (l/s)
14, diffusion pump speed calculation formula:
S=Q/P=(K·n)/(P·t) (l/s)
Where: the pumping rate of the S-test pump (l/s)
N-dropper oil column rise (cells)
T- The time required for the oil column to rise n times (seconds)
P - Pressure measured near the pump port (Torr)
K-dropper coefficient (Torr · liters/second)
K=V0·(L/n)·(Υ0/Υm)+PaΔVt
The original volume of V0-dropper and vacuum hose (l)
Length of L-dropper scale (mm)
The number of cells in the n-dropper scale
Î¥0-specific gravity of oil (g/cm3)
Î¥m-specific gravity of mercury (g/cm3)
Pa - Local Atmospheric Pressure (Torr)
â–³Vt - The corresponding volume of the cell on the scale of the dropper (in liters/division)
15. Calculation formula of geometric pumping speed of rotary vane vacuum pump:
S=πZnLKv(D2-d2)/(24×104)(l/s)
Where: Z is the number of rotors, n is the rotation speed (rpm), L is the length of the pump chamber, D is the diameter of the pump chamber, d is the diameter of the rotor (cm), Kv is the volume utilization factor (generally 95%).
16, O-type rubber tank depth B = 0.7D
D is rubber diameter, slot width C = 1.6B
17, the square rubber groove depth B = 0.8A
A is the square rubber side length, slot width C=1.67B
1. Boyle's Law Volume V, Pressure P, P · V = Constant A certain mass of gas. When the temperature is constant, the pressure of the gas is inversely proportional to the volume of the gas.